Almanac for Roque de los Muchachos:
long.   1 11 31 (h.m.s) W, lat.  28 45.5 (d.m), elev.  2326 m
pseudo-Greenwich Daylight Savings Time assumed from 2 AM on
1998 Mar 29 to 2 AM on 1998 Sep 27; standard zone =   0 hrs W

For the night of: Sat, 1998 May 9 ---> Sun, 1998 May 10
Local midnight = 1998 May 9, 23 hr UT, or JD 2450943.458
Local Mean Sidereal Time at midnight =  12 58 41.4

Sunset ( 2326 m horizon):   20 59 GDT; Sunrise:    7 16 GDT
Evening twilight:   22 19 GDT;  LMST at evening twilight:   11 18
Morning twilight:    5 56 GDT;  LMST at morning twilight:   18 56
12-degr twilight:  21 48 GDT -->   6 28 GDT; night center:    2 08 GDT

Moonrise:   19 03 GDT   
Moon at civil midnight: illuminated fraction 0.975
1.6 days until full moon, RA and dec:  14 01 40,  -8 33.5

The sun is down for 10.3 hr;  7.6 hr from eve->morn 18 deg twilight.
Bright all night (moon up from evening to morning twilight).